Historically, a significant portion of piston design and development work for diesel engines has involved ways to minimize piston metal temperatures through various cooling arrangements such as incorporating cast cooling passages in critical temperature areas, jet spray and splash cooling of the piston undercrown, entrapment of a cooling medium in "cocktail shaker" cavities for cyclic impingement on the piston inside surface, and so forth. Such arrangements have been aimed at increasing heat transfer from critical areas of the piston metal to minimize piston temperatures and decrease thermal stress levels to values compatible with material yield strengths.
In a contrary vein, some work has also been done to provide pistons with insulating means for limiting the loss of heat from the combustion chamber area to other portions of the engine. Such arrangements have been proposed for increasing engine operating efficiency by reducing lost heat as well as, in some cases, to improve combustion and reduce undesirable exhaust emissions.
While extensive commercial use has been made of oil cooled high output diesel engines pistons of the sort first referred to, it is believed that few, if any, satisfactory commercial embodiments of insulated combustion heat saving pistons have been utilized.